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H. Shim, E. Krahn, A. Rao, C.-K. Chen; Involvement of RGS7 And RGS11 in ERG b-wave. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1024.
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The ERG of Gβ5 knockout (Gβ5-/-) mouse lacks the b-wave component due to the post-photoreceptoral loss of Gβ5-S. The four members of the R7 subfamily of the Regulators of G-protein Signaling (RGS), namely, RGS6, -7, -9, and -11, are down-regulated in Gβ5-/- mice to near or below the detection level. To gain insight into how Gβ5-S contributes to the generation of ERG b-wave, we characterize mutant mouse strains where RGS11 and/or RGS7 genes are inactivated by targeted deletion.
The RGS7- or RGS11-targeted mutant mouse lines, available from the Mutant Mouse Regional Resource Centers, are crossed to generate the double mutant line named SG711. ERG is recorded under scotopic and photopic conditions, bridged by a 10-minute light adaptation period at 30 cd/m2 background intensity. The implicit times and amplitudes of both a- and b-waves and the prominent oscillation potentials are analyzed at various flash intensities. Wild type and mutant RGS7 cDNAs are amplified by RT-PCR and recombinant proteins are produced in H5 cells with or without Gβ5. Protein levels are determined by Western blotting. Protein localization is determined by immunocytochemistry.
Both RGS7 and RGS11 are co-localized to dendritic tips of ON-bipolar cells with Go. The ERG of the SG711 mice shows a markedly delayed b-wave. In contrast, RGS11 knockout (RGS11-/-) mice show a moderately delayed ERG b-wave, while the homozygous RGS7 mutant mice show ERG responses indistinguishable from those of the sibling wild type controls. The RGS7 mutant mice are not null but express a truncated RGS7 protein lacking 33 amino acids due to the deletion of exon-10. When expressed ectopically in insect cells, wild type RGS7 can be expressed without co-expressing Gβ5-S but the truncated RGS7 protein is not stable by itself. The level of Gβ5-S in the SG711 mouse retinas, when normalized to that of the photoreceptor-specific Gβ5-L, is significantly less than the controls. Gβ5-S can be found in the dendritic tips of the ON-bipolar cells in the SG711 mouse retinas.
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